This blog is devoted to the discussion of all aspects of synthetic organic chemistry and related sciences. Curly Arrow is run by a synthetic organic chemist based in Copenhagen, Denmark. Contributions from readers are always welcome and should be emailed to curlyarrow@gmail.com

Wednesday, December 20, 2006

NMR and Whisky

I have a real weakness for single malt whisky so when I started my PhD in Cambridge I was pleasantly surprised to see that the NMR machines were named after Scotch single malt whiskies: Aberlour, Cragganmore, Glengrant, Glenlivet and Laphroaig. At the same time as I started my PhD they began the process of acquiring and installing a 700 MHz Bruker Cryo probe monster. Obviously this new addition to the collection of NMR machines needed a name. I'm a big fan of the Arran single malt whisky which at the time was the youngest Scottish distillery. So I thought that Arran would be an appropriate name for the departments youngest NMR machine and I suggested it to the NMR guys. I even went as far as purchasing them a little box with a selection of Arran malts. Clearly, the guys liked the idea and to my great pleasure the machine was named Arran. Here's a picture of the NMR people (from left: Duncan, Andrew and Brian) with Arran and a selection of miniature Arran bottles:

Not only do they give their NMR machines great names but they also provide a most excellent NMR service. These guys actually like what they do and will go to great lengths to help you out. The best NMR department (by orders of magnitude) that I have experienced so far. Anyway, after Arran was named we obviously had to run some 1 and 2D NMR of the Arran malt on Arran to see what the spectrum of a tasty single malt looks like. Below the HMQC spectrum of the organic phase after an extraction of Arran malt with dichloromethane is shown. We didn't use the regular stuff but a limited edition single cask Arran malt (Bottle no. 125 of 348, 58.7%, distilled 18/7-1997).

Yes a complete waste of time and resources but it was fun. We took the photo above and a bunch of the NMR spectra and sent it to Isle of Arran Distillers with a letter explaining matters and it turned out that the guys at the distillery really liked the story. They showed their appreciation by sending us a bottle of Arran malt each - nice guys! D!

Japanese have done some extensive NMR and GC/MS research on identification of flavor components of single malts. Despite of all this research , their artificialy-flavored nipponese scotch brands stil taste like murder.

Another practical application of this kind of research is the flavoring in butterscotch-pudding and egg nog. It contains a mysterious substance called whisky lactone :) and i think this one actualy comes from oak barrels rather then peat-smoked malt.

There was a paper in Org Lett about 2 years ago about taking NMR 1-H spectra without lock and among the samples they run was also bourbon whiskey. I think they were using their NMR method as an assay for determining alcohol content in liquers.

Yo Milkshake, there's nothing mysterious about Whisky lactone aka Oak lactone aka (4S,5S)- and (4S,5R)-5-butyl-4-methyl-4,5-dihydro-2(3H)-furanone except for how it's generated during the oak maturation process. A whole range of different precursors have been suggested, in particular ring opened version that are glycosylated or acylated on the secondary alcohol. Of the two Oak lactone isomers the (4S,5S)-isomer is considered the more important from a sensory point of view. It is believed to be one of the compounds that impart coconut- and vanilla-like nuances to wine. It can be purchased in buckets and is used widely in the manufacture of cheap scotch whiskies to improve the taste (it still tastes like shite in my opinion). By the way the blended japanese whiskies do indeed make you blind and throw up. However, the Japanese make awesome single malt whiskies that go very well with sushi. The only problem is that they are very expensive compared to their scottish counterparts. D!

"Despite of all this research , their artificialy-flavored nipponese scotch brands stil taste like murder."You might want to revise that stereotype now that the Japanese are winning some of the top whisky awards internationally.